Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery module having a plurality of battery cells electrically connected to each other because high power and large capacity are necessary for the middle or large-sized devices.
Preferably, a middle or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, the manufacturing cost of the pouch-shaped battery is low, and it is easy to modify the shape of the pouch-shaped battery.
Meanwhile, in order for the middle or large-sized battery module to provide power and capacity required by a specific apparatus or device, it is necessary for the middle or large-sized battery module to be configured to have a structure in which a plurality of battery cells is electrically connected to each other in series and the battery cells are stable against external force.
Consequently, in a case in which a middle or large-sized battery module is configured using a plurality of battery cells, a plurality of members for mechanical fastening and electrical connection between the battery cells is generally needed and, as a result, a process for assembling the mechanical fastening and electrical connection members is very complicated. Furthermore, there is needed a space for coupling, welding, or soldering the mechanical fastening and electrical connection members with the result that the total size of the system is increased. The increase in size of the system is not preferred in the aspect of the spatial limit of an apparatus or device in which the middle or large-sized battery module is installed. Moreover, the middle or large-sized battery module must be configured to have a more compact structure such that the middle or large-sized battery module can be effectively installed in a limited inner space, such as a vehicle.
In addition, the battery cells constituting the middle or large-sized battery module may be secondary batteries which can be charged and discharged. Consequently, a large amount of heat is generated from the battery cells during operation of the battery cells. If the heat, generated from the battery cells, is not effectively removed therefrom, deterioration of the battery cells is accelerated. According to circumstances, the battery cells may catch fire or explode. For this reason, it is required to efficiently dissipate heat from the battery cells. To this end, it is necessary to provide a flow channel. However, such a flow channel increases the size of the battery module.
In relation to this issue, structures of some conventional middle or large-sized battery modules will hereinafter be described.
Japanese Registered Patent No. 3355958 discloses a middle- or large-sized battery module including a plurality of battery cells stacked in a limited space, such as a vehicle, configured to have a structure in which protrusions defining a coolant flow channel are formed at the outside of each battery cell, such that a coolant cools the battery cells while the coolant passes through each stacked battery group after the coolant is introduced into gaps defined between the battery groups, in order to prevent reduction in cooling efficiency of the coolant which may be caused when, in a state in which the temperature of the coolant increases as the coolant passes through one stacked battery group, the coolant passes through another stacked battery group. The battery cells used in this patent are alkaline batteries such as nickel-metal hydride batteries. External shapes of the alkaline batteries exhibit high mechanical strength. Consequently, plates are disposed at opposite sides of a stack constituted by a plurality of battery cells and the plates are fixed by bands to configure a middle or large-sized battery module.
The battery cells disposed in the above patent has an advantage in that the battery cells can be easily stacked due in terms of external shapes thereof in addition to the structural characteristics to improve cooling efficiency. However, the battery cells disposed in the above patent has a disadvantage in that the battery cells have large volume and weight due to external shapes to provide high mechanical strength.
In addition, Japanese Patent Application Publication No. 2005-050616 discloses a middle or large-sized battery module installed in a large-sized vehicle, such as a bus, configured to have a structure in which the battery module includes a lower rack in which two battery packs are disposed and an upper rack in which two battery packs are disposed, a stand member of the lower rack and a stand member of the upper rack are suspended from a body of the vehicle via a suspension member of the lower rack and a suspension member of the upper rack, the stand members exhibit high strength, and the suspension members exhibit low strength, thereby improving safety of the battery module against external force applied to the battery module due to a vehicle crash.
In the above-described middle or large-sized battery module, a plurality of racks is used to improve safety of the vehicle when a vehicle crash occurs. However, two complicated racks are provided to install a total of four battery packs with the result that volume and weight of the battery module are increased. Consequently, it is technically difficult to configure the battery module such that the battery module has a compact structure.
Meanwhile, a battery module assembly is a structural body constituted by combining a plurality of battery cells and, therefore, safety and operational efficiency of the battery module assembly are greatly lowered when some of the battery cells suffer from overvoltage, overcurrent, or overheating. For this reason, means to sense and control such overvoltage, overcurrent, or overheating are needed. Consequently, voltage sensors, temperature sensors, etc. are connected to the respective battery cells to check and control operational states of the battery cells in real time or at predetermined intervals. Installation or connection of such sensing means and control means very complicate a process of assembling the battery module. Furthermore, a plurality of wires is needed to install or connect the sensing means and the control means with the result that a short circuit may occur in the battery module.
In particular, voltage sensing must be performed at electrical connection regions, such as series connection regions. As a result, a battery module or a battery module assembly manufactured by connecting a plurality of battery cells may have a very complicated structure as a whole.
Therefore, there is a high necessity for a battery module, the structure of which is compact, structural stability of which is high, and which is configured such that a sensing assembly can be efficiently assembled while solving the above problems.
In addition, there is a high necessity for a battery module assembly which can be configured using a plurality of battery modules with high assembly efficiency.